Expert: Paul Karthaeuser - 1/8/2012

Question
We have a one year old fireplace, in a chase on an outside wall. Outside of chase is insulated with spray on foam. Nearly flat roof, so only pipe above the roof. A small cold outside air vent is in the outer chase wall for air to the firebox, but it is not controlled. When nights are in the 20s or colder, we apparently get condensation/freezing water between the two flue pipe layers, because it melts in the day if it warms up with sun, and runs out the front of the fireplace front air circulation vent above the firebox. Our contractor is at a loss. What can we do for this?

Answer
David,

Honestly, I am not convinced that is the source of your problem.  Have you done or had a professional Fireplace and Chimney Inspector done a thorough inspection of the system?  I have seen this situation happen more commonly due to a leaking chase cover atop the chimney chase than anything else. Often times the chase cover is leaking or else it's the storm collar around the chimney pipe itself at the top of the chase that is either unsealed or has rusted and is leaking.  The water will enter the chase top, run down the pipe and gather/pool atop the firebox and spills into the upper air louvers.  Sometimes homeowners have reported a metallic pinging sound during rain storms from the water hitting the top of the firebox within the chase. Obviously yours has not likely rusted given the one year old age but I have seen far too many fireplace systems installed incorrectly from day one. Nonetheless, I have heard very few times of condensation problems related to factory built fireplace and chimney systems resulting in what you are describing.  You are describing a significant volume of water too.  I don't know many details of your home/installation and so you are welcome to send me pictures if you like (paul@thechimneyguys.com).  I wonder how much chimney is protruding from the top of the chase for one thing.
I would defer to a professional fireplace and chimney inspector, particularly one that is F.I. R.E. Certified which is an organization that certifies individuals in the area of Inspection specifically in the hearth appliance and chimney field.  You can go to http://www.f-i-r-e-service.com/Landing-Continuing-Education.php  and find their contact info on this page to see if there is an Inspector in your area.  Otherwise contact a chimney contracting company in your area but be sure to do the research and inquire as to their credentials as all chimney companies are not created equal.  That is to say that unfortunately there are no requirements for education in this profession and likely anyone who has taken the time to pursue some certifications is more qualified and educated in the area and will be better able to help solve your problem.
Again, I will be happy to answer any follow up questions from you or view any pictures you'd like to send.

I just had a final thought too...Do you have gas or propane heat and does the vent run through this chase too?  Does it terminate at the same height as the fireplace chimney?

I hope I have been helpful.  Thank you.

Paul